Uncluttered Habitats Research Articles

Ecological Morphology of Neotropical Bat Wing Structures.

Morphology has a direct influence on animal fitness. Studies addressing the identification of patterns and variations across several guilds are fundamental in ecomorphological research. Wings are the core of ecological morphology in bats; nevertheless, individual bones and structures that support the wing, including metacarpals, phalanges and the length of digits, have rarely been the subject of comprehensive research when studying wing morphology. Here, I analyzed morphological variations of wing structures across 11 bat guilds and how individual bone structures are correlated to diet, foraging mode and habitat use. I obtained wing measurements from 1512 voucher specimens of 97 species. All the specimens analyzed came from the Mammalian Collection at the Museo Javeriano de Historia Natural of Pontificia Universidad Javeriana (MPUJ-MAMM) (Bogotá, Colombia). Positive correlations between size and the length of the third and fifth digit were detected. Bat guilds that capture their preys using aerial strategy in uncluttered habitats had longer third digits but short fifth digits compared to guilds that rely on gleaning strategy and forage in highly cluttered space. Although terminal phalanges were shown to be important structures for guild classification, metacarpals were strongly related to aerial foragers from uncluttered habitats because of their potential role in flight performance and ecological adaptations. Results show that habitat use, as well as foraging mode, are reflected in wing structures. Different wing traits to those evaluated in this study should be considered to better understand the ecological interactions, foraging strategy, wing adaptations, and flight performance in Neotropical bats.

Dietary Composition, Resource Partitioning and Trophic Niche Overlap in Three Forest Foliage-Gleaning Bats in Central Europe

A diverse syntopic bat community was studied in Central Europe. The study was primarily aimed at forest bats utilizing a foliage-gleaning foraging strategy (Myotis nattereri, M. bechsteinii and Plecotus auritus). The results indicated the foliage-gleaning foraging strategy and the effective resource partitioning. Once a certain diet item comprises an important food resource for one bat species, it is usually exploited much less by the other two bat species, and despite important seasonal dietary changes this pattern lasts throughout the entire season. Dietary composition varies more among the entire guild of forest foliage-gleaning bats than it does between these species and their morphological siblings or evolutionarily related species (e.g., Plecotus auritus vs. P. austriacus or Barbastella barbastellus, Myotis nattereri vs. M. emarginatus). The results are not fully consistent with the predictions of sensory ecology, which presume that bats with longer ears feed more frequently on prey that generates sound. The results do not support the hypothesis that rare bats exploit a narrower range of prey. The relatively rare M. bechsteinii has a wider trophic niche, whereas the more common P. auritus exploits a narrower range of prey. Comparison of dietary composition and morphological and echolocation parameters indicates that larger species feed on harder prey, species with longer ears are moth-eating specialists and species with a higher call intensity exploit small dipterans, probably in uncluttered habitats.

Echolocation Calls of Bats from Madeira Island: Acoustic Characterization and Implications for Surveys

Acoustic surveys represent a powerful tool to assess bat distribution and habitat preferences and are widely applicable to monitoring and conservation schemes. However, their correct application requires the development of robust and reliable identification procedures. Little information is available on the bats of Madeira Island (Portugal), particularly their ecological requirements, distribution and population trends, and proper guidelines for their monitoring and conservation have yet to be defined. In this study, we present the first analysis of echolocation calls from species occurring on the island to provide a tool for bat identification during acoustic surveys. Seven hundred and ninety one time-expanded recordings of search phase echolocation calls in cluttered and uncluttered habitats of the Macaronesia endemic pipistrelle Pipistrellus maderensis, Madeira Leisler's bat Nyctalus leisleri verrucosus and grey long-eared bat Plecotus austriacus were analysed and an acoustic repertoire with their temp...

Echolocation calls in Central American emballonurid bats: signal design and call frequency alternation

AbstractIn southern Central America, 10 species of emballonurid bats occur, which are all aerial insectivores: some hunt flying insects preferably away from vegetation in open space, others hunt in edge space near vegetation and one species forages mainly over water. We present a search call design of each species and link signal structure to foraging habitat. All emballonurid bats use a similar type of echolocation call that consists of a central, narrowband component and one or two short, frequency‐modulated sweeps. All calls are multi‐harmonic, generally with most energy concentrated in the second harmonic. The design of search calls is closely related to habitat type, in particular to distance of clutter. Emballonurid bats foraging in edge space near vegetation and over water used higher frequencies, shorter call durations and shorter pulse intervals compared with species mostly hunting in open, uncluttered habitats. Peak frequency correlated negatively with body size. Regular frequency alternation between subsequent calls was typical in the search sequences of four out of 10 species. We discuss several hypotheses regarding the possible role of this frequency alternation, including species identification and partitioning of acoustic channels. Furthermore, we propose a model of how frequency alternation could increase the maximum detection distance of obstacles by marking search calls with different frequencies.

Bat Activity in a Forest Landscape of Central Massachusetts

Nine species of bat are known to occur across the six New England states, but most aspects of their natural history, such as foraging habitat use, are poorly understood. Recent published research has documented the importance of still-water habitats as foci of bat flight activity. To better understand and document habitat use in southern New England, we used the AnaBat II acoustical monitoring system to assess species composition and relative levels of summer flight activity. Active acoustic surveys were conducted in six habitat types on the Quabbin Reservation in central Massachusetts in 2003 and 2004. Bat flight activity, as measured by numbers of echolocation call sequences, was high, with an average of 24 search-phase and 4 feeding-buzz calls per 20-minute survey period. Myotis lucifugus (little brown bat) was the most commonly recorded species. Bat flight activity was high over all still-water habitats, but greatest over large ponds. Large-bodied bats, such as Eptesicus fuscus (big brown bat), were recorded more often in open, structurally uncluttered habitats. Of the small-bodied bats, little brown bats were ubiquitous, whereas Myotis septentrionalis (northern myotis) was most common in structurally cluttered habitats of seasonal forest (vernal) pools and along forest streams. Generalized habitat associations among the bat species we recorded are similar to those reported for other New England forest sites. The Quabbin Reservation is an excellent site to continue examining bat-habitat relationships because of the abundance and diversity of aquatic habitats, in both cluttered closed-canopy and uncluttered open-canopy settings.

Relating bat species presence to simple habitat measures in a central Appalachian forest

We actively sampled the bat community at 63 sites using detection and non-detection metrics on the Fernow Experimental Forest (FEF) in the central Appalachians of West Virginia using Anabat acoustical equipment May–June 2001–2003 to relate species presence to simple habitat measures such as proximity to riparian areas, forest canopy cover, forest canopy gap width, and forest canopy height. We acoustically detected eight species on the FEF, including the endangered Myotis sodalis. The presence of Lasiurus cinereus, M. lucifugus, M. sodalis, and Pipistrellus subflavus was associated more with riparian areas than upland areas. Both univariate comparisons and multiple logistic regression modeling showed that the probability that clutter-adapted foraging species such as M. septentrionalis and M. sodalis would be detected was greater as forest canopy cover increased or forest canopy gap size decreased, whereas the opposite was true for open-adapted foraging species such as Eptesicus fuscus and L. cinereus. The overall proportion of unidentifiable bat echolocation sequences to those identified to species was related to upland sites with increasing forest canopy cover indicating some sampling bias between cluttered and uncluttered habitats. However, given sufficient sample points, bat community surveys using acoustical detection show the ability to quickly develop generalized habitat associations for rugged areas such as the central Appalachians where traditional mist-net survey efforts often are logistically difficult and are lacking in scope. Moreover, these acoustical surveys also could lend themselves to species-specific predictive mapping of foraging habitat as well as allowing researchers to formulate testable hypotheses about detailed bat habitat relationships to be definitively tested with radio-telemetry techniques.

Variability in echolocation calls ofPipistrellus pygmaeus (Chiroptera: Vespertilionidae) during search flight in different habitats

The changes in echolocation behaviour and the structure of calls ofPipistrellus pygmaeus (Leach, 1825) were studied in different habitats of a floodplain forest in south-eastern Moravia (Czech Republic) in 2001–2002. Calls (403 observations) were recorded in different sites between April and mid June (before weaning) using a time expansion bat-detector. Three signals per individual were analysed and descriptive statistics of variables of calls were presented. Association of signal types with habitat structure (cluttered, side-cluttered, semi-cluttered and uncluttered space) was found in echolocation sequences of the search phase of flight.P. pygmaeus used mainly narrowband signals (bandwidths less than 15 kHz) in uncluttered space and wideband signals (more than 15 kHz) in cluttered space. Almost 6% of the inter pulse intervals of signals were twice (or more) longer than usual inter pulse intervals (mainly in uncluttered space). In general, temporal variables of signals reached higher values in uncluttered spaces (except for inter pulse interval) than in cluttered ones. On the contrary, spectral variables of signals reached lower values in uncluttered habitats in comparison with cluttered ones. In addition, the signals were less variable in open spaces while in cluttered and partly-cluttered habitats different and higher variability was found. We also studied the accuracy of identification of pipistrelles by call parameters and possible misidentifications in relation to habitat structure. Multivariate discriminant analyses were carried out on the time and frequency parameters of calls produced by pipistrelles.

EFFECTS OF CLUTTER ON ECHOLOCATION CALL STRUCTURE OF MYOTIS SEPTENTRIONALIS AND M. LUCIFUGUS

The structure of echolocation calls, and the distance over which bats perceive their environment, varies with the amount of structural clutter through which they are flying. Clutter and species had significant effects on the frequency-time characteristics of search-phase echolocation calls of northern long-eared (Myotis septentrionalis) and little brown bats (M. lucifugus). We tested an a priori derived model that predicted the pattern of differences in echolocation call variable values among clutter categories would provide insight into the relative maximum distances that bat species could perceive using echolocation. Specifically, the model predicted that species adapted to flying and foraging in cluttered habitats would have a shorter maximum perceptual distance than species adapted to flying and foraging in uncluttered habitats. The results supported this model and suggest the clutter-adapted M. septentrionalis had a shorter maximum perceptual distance than M. lucifugus, a species known to forage in a variety of habitats but mainly in uncluttered areas (i.e., over water). Using calls as the sampling unit, a neural network correctly classified >94% of the echolocation calls to species in high clutter. In medium and low clutter, >82% of the calls were correctly classified to species; however >90% correct classification was achieved by leaving <30% of calls unclassified. Researchers should develop clutter-specific call libraries to improve species classification accuracy for echolocation calls.

Effect of acoustic clutter on prey detection by bats.

Bats that capture animal prey from substrates often emit characteristic echolocation calls that are short-duration, frequency-modulated (FM) and broadband. Such calls seem to be suited to locating prey in uncluttered habitats, including flying prey, but may be less effective for finding prey among cluttered backgrounds because echoes reflecting from the substrate mask the acoustic signature of prey. Perhaps these call designs serve primarily for spatial orientation. Furthermore, it has been unclear whether the acoustic image conveyed by FM echoes enables fine texture discrimination, or whether gleaning bats that forage in echo-cluttering environments must locate prey by using other cues, such as prey-generated sounds. Here we show that two species of insectivorous gleaning bats perform badly when compelled to detect silent and immobile prey in clutter, but are very efficient at capturing noisy prey items among highly cluttered backgrounds, and both dead or live prey in uncluttered habitats. These findings suggest that the short, broadband FM echolocation calls associated with gleaning bats are not adapted to detecting prey in clutter.

Bat communities in a fragmented forest landscape on the south-west slopes of New South Wales, Australia

Ultrasonic detectors were used to compare bat activity and species richness at replicated continuous and isolated forests, large and small remnants, corridors and open areas on the south-west slopes of New South Wales, Australia. The habitat matrix in this area consists primarily of agricultural land interspersed with indigenous forest remnants and pine plantations. Ten taxa of bat were recorded, with the fewest in corridors. A multivariate analysis revealed that a gradient in forest area, habitat diversity and structural complexity was the most consistent predictor of activity for four taxa ( C. morio, Nyctophilus spp., V. regulus and F. tasmaniensis), suggesting that these are sensitive to the effects of forest fragmentation. Six species ( N. australis, M. planiceps l.p., C. gouldii, M. schreibersii, V. darlingtoni, V. vulturnus) appeared tolerant of fragmentation and were not sensitive to isolation effects. Most tolerant species were active over open areas and probably used resources in the agricultural mosaic. Typically they were fast flying, low manoeuvrability species which are predicted to forage in uncluttered habitats. Although total activity in small remnants and corridors was as great as that in large forests continuous with a 690 000 ha national park, feeding activity was greatest in continuous forests, suggesting that larger forests with high habitat diversity offered more foraging opportunities. Despite providing fewer feeding opportunities, remnants represent an important conservation resource for bats because activity is concentrated here and they provide potential roost sites. Activity of each species in open areas was not significantly lower than that in corridors (non-riparian), suggesting that corridors were not used regularly by bats to move through the landscape. More detailed studies of the movements of species identified as sensitive to fragmentation would help to explain how fragmentation affects these species and thus what measures are required to improve their conservation.

Plasticity in echolocation signals of European pipistrelle bats in search flight: implications for habitat use and prey detection

We studied the echolocation and hunting behavior of three aerial insectivorous species of bats (Vespertilionidae: Pipistrellus) in the field in order to characterize the signals used by the bats and to determine how call structure varies in relation to habitat structure (“uncluttered” versus “cluttered” space). We documented free-flying, naturally foraging wild pipistrelles in various habitats using multiflash stereophotography combined with simultaneous sound recordings. Then we reconstructed the bat's flight position in three-dimensional space and correlated it with the corresponding echolocation sequences. In all three species of pipistrelles, signal structure varied substantially. In echolocation sequences of the search phase we found a consistent association of signal types with habitat types. In uncluttered habitats (obstacles more than 5 m from the bat) pipistrelles emitted almost exclusively narrowband signals with bandwidths less than 15 kHz. In cluttered habitats (obstacles less than 5 m from the bat) they switched to signals with bandwidths of more than 15 kHz. Wideband signals were also used when the bats were turning in cluttered and uncluttered spaces and for an instant after turning away from obstacles. Prey detection occured only when the outgoing signal did not overlap with the returning echo from potential prey. The bats also avoided overlap of echoes from potential prey and obstacles. Based on the results of this study, we propose an overlap-free “window” within which pipistrelles may detect potential prey and which allows predictions of minimum distances to prey and clutter-producing objects.

Variation in Habitat Use and Prey Selection by Yuma Bats, Myotis yumanensis

The purpose of our study was to assess variation in habitat use and prey selection by Myotis yumanensis in British Columbia. In particular we tested the hypothesis that habitat use and resulting prey choice are constant among different reproductive and age classes. We light tagged 115 individuals and observed their foraging activity for a total of 218 min on 16 nights from May to September 1989. The four reproductive and age classes (pregnant, lactating, post-lactating, juvenile) all predominantly foraged within open, uncluttered habitats over land and low over water. Dietary variation suggests this species forages opportunistically on aquatic insects with changes in diet reflecting changes in availability.